a function with same name and function alrdy exist?

[Hartmann]

Im getting an error saying that a function with the same name and functions alrd exist. cna you help. here is my script

void OnStart()
{
AddEntityCollideCallback("Player", "PlayerCollide", "MonsterFunction", true, 1);
AddUseItemCallback("", "key_4", "castle_no_grav_1", "KeyOnDoor", true);
AddUseItemCallback("", "bone_saw_1", "wooden_boards_block_1", "DestroyParticleSystem", true);
AddTimer("StopLook", 4, "LookAtSaw");
}

void DestroyParticleSystem(string& asName)
{
PlaySoundAtEntity("", "saw", "wooden_boards_block_1", 0.0f, true);
RemoveItem("bone_saw_1");
}


void MonsterFunction(string &in asParent, string &in asChild, int alState)
{
SetEntityActive("servant_grunt_1", true);
}

void KeyOnDoor(string &in asItem, string &in asEntity)
{
SetSwingDoorLocked("castle_no_grav_1", false, true);
PlaySoundAtEntity("", "unlock_door", "castle_no_grav_1", 0.0f, true);
RemoveItem("key_4");
}

////////////////////////////
// Run when leaving map
void OnLeave()
{

}

void LookAtSaw(string &in asTimer)
{
StopPlayerLookAt();
}